Well as far as cats vs yorkies go, I think cats are much more agile (you know he old story - cats always land on their feet). I know when I first got my yorkie there were a couple of times I bent to put her down and didn't quite bend over far enough and she kinda tumbled when she hit the ground
. She is my first tiny dog and I've had lots of cats and I just wasn't used to handling a little dog. Mine isn't all that small (almost 6 lbs) but some of the people on this board describe broken legs from jumping off a bed or couch. Have you even heard of that happening to a cat?
As far as kids go, your kids may be very conscientious and gentle. However, lots of kids are not that gentle all the time and can be a bit clumsy.